Maha Mudra is the first stage of Maha Bandha. After pressing anal region with left heel,place the right foot on left thaigh.
Contract the anal and Peri-anal muscles.
Draw the Apana Vayu up-wards,take deep breath,do kumbhaka, then make Jalandhara Bandha and Sambhavi Mudra.Retain the posture as along as you can.Then do rechaka.
As it contains Maha Mudra,Jalandhara Bandha, & Sambhavi Mudra,you can assume how many advantages this Maha Bandha can facilitate the Sadhaka. This is the same reason, why this posture is called as MAHA BANDHA.